SAT / ACT Prep Online Guides and Tips

The Best ACT Diagnostic Test and How to Use It

Posted by Christine Sarikas | May 24, 2018 12:00:00 PM

ACT Strategies



An ACT diagnostic test is an important part of your ACT prep, but there’s a lot more to it than just answering a few questions and seeing how you score. A diagnostic test can be one of the best tools for shaping your ACT study plan, but you need to know where to find the right ones and how to take them properly.

In this guide, we explain what an ACT diagnostic test is, why it’s such an important study tool, where you can find the best diagnostic tests, and every step you should take to get as much valuable info from your diagnostic test as possible.


What’s an ACT Diagnostic Test and How Can It Help You?

An ACT diagnostic test is a practice test that you take at the beginning of your studying. This is more than just any practice test though. You can use your diagnostic test results to figure out your strengths and weaknesses on the ACT, how well you’re currently scoring, and how much you need to improve. All of these are key pieces of information for developing an effective study plan that’ll get you the ACT results you're aiming for.

Without an ACT diagnostic test, you’ll find it much harder to study effectively for the ACT because you won’t know how much progress you need to make or which areas you should be focusing on. We recommend that every person studying for the ACT take a diagnostic test early in their prep.


What Are the Best ACT Diagnostic Tests?

There are lots of free ACT diagnostic tests out there, but the best ones to take will always be official ACT practice tests. Official ACT practice tests are retired real ACTs, so they'll be very similar to the ACT you see on test day. This is key because, if your diagnostic test isn’t a good replica of the real ACT, your diagnostic test results won’t give you a very accurate idea of how well you’d score on the ACT, so you could end up studying too little, studying too much, or studying the wrong subjects.

It’s key that your diagnostic test mimics the difficulty, content, and format of the real ACT. Fortunately, this is easy to do. There are lots of high-quality and free ACT diagnostic test pdfs out there. We actually have links to every free and official ACT practice test available online. Use one of these for your diagnostic.

If you’re looking for a shorter free ACT diagnostic test, your options are somewhat limited. There are many unofficial practice quizzes available, but we don’t recommend them since they aren’t as high-quality as official resources. ACT Inc. offers short quizzes for each section of the exam. There are five quizzes for each exam section, and each quiz has five questions.

If you choose to take some of these quizzes for your diagnostic test, know that you won’t be able to get an accurate score estimate from them since their format is so different from the format of the actual ACT. Instead, you can use the quizzes to get a general idea of the areas where you’re doing well and where you need to study more.


How Should You Take an ACT Diagnostic Test?

When you take your ACT diagnostic exam, it’s crucial to mimic real testing conditions as closely as possible so that you can get the most accurate score from your diagnostic. If you give yourself more breaks or time than you’d get on the real test, your diagnostic test results won’t be as useful.

Here are the main rules you should follow when taking your diagnostic:

  • Take the test with pencil and paper (You’ll be taking the real ACT this way, so we don’t recommend taking your ACT diagnostic online.)
  • Take the test all in one sitting
  • Keep strict timing for each section (don’t give yourself even one minute extra to complete a section!)
  • Use only the breaks you’d get on the official exam (10 minutes after the Math section and 5 minutes before the Writing section if you’re taking it)
  • Minimize distractions (no music, TV, people talking in the room, etc.)

For a more in-depth look at the best way to take ACT practice tests, check out our guide specifically on the topic.




How Should You Analyze Your ACT Diagnostic Test Results? Big Picture Questions

After you’ve taken your diagnostic test, you’ll need to break down your test results to understand exactly what you need to work on and where you can improve. Here are three of the first questions you should ask yourself.


Which Sections Were Your Best? Your Worst?

After you’ve looked at your overall score, review your section scores for English, Math, Reading, and Science. How do they compare to each other? Are some section scores significantly higher than others? Students often divide their study time equally between each of the ACT sections or read entire prep books all the way through to make sure they’re learning everything they can.

However, if your section scores vary widely, this isn’t the most efficient use of your time. You want to concentrate more study time on the section(s) where you need to make the biggest improvement. So if, say, your Science score is the lowest of your section scores, you’ll want to spend more time studying Science than you would studying for Math, English, or Reading.


Which Types of Questions Did You Struggle the Most With?

When your review the results of your ACT diagnostic test, you’ll be able to see not only which sections you were stronger or weaker on, but also which question types you struggled with the most. For example, the Science section has three different types of questions. Maybe you did pretty well on Data Representation questions but struggled on the Conflicting Viewpoints questions.

The more detailed your analysis is, the more it’ll help you develop a study plan that effectively targets your weaknesses and helps you raise your score. We have guides that explain the different question types you’ll see on each section of the ACT: English, Math, Reading, and Science.


Were You Pressed for Time?

The ACT is strictly timed, and if you ran out of time on any section of your diagnostic, that’s absolutely something you need to focus on during your studying. Leaving just a few questions blank on each section because you didn’t have time to answer them can have a major impact on your score.

The ACT expects you to answer many questions in a limited amount of time, and many students struggle with completing the test within the time limits. If you felt you knew most of the information being tested but just didn’t have the time to answer all the questions, working on your timing skills will be key to improving your ACT score.




How Should You Analyze Your ACT Diagnostic Test Results? Nitty Gritty Questions

Once you’ve looked at the big picture info you got from your diagnostic, it’s time for a more detailed analysis. To do this, you should go through every question you got wrong (or just guessed on) on your diagnostic ACT and figure out why you answered it incorrectly.

For each question you answered incorrectly, think about why you got it wrong. There are generally four reasons people make mistakes on exams:

  • Time Issue: You didn’t have enough time to answer the question.
  • Question Comprehension Issue: You knew the information needed to correctly solve the question, but the question was too complicated, you weren’t sure what exactly was being asked, or you were tricked by the question.
  • Procedural/Content Issue: You weren’t sure how to solve a question, or you didn’t have the background knowledge needed to solve it.
  • Careless Error: You knew how to solve the question, but you made a silly mistake that caused you to choose the wrong answer.

We give detailed explanations for how to overcome each of these issues in our guide to going over ACT questions you got wrong, but below are key solutions for each of the four issues.


Time Issue

To get a better handle of the ACT’s timing and maximize the amount of time you get on each section, there are several techniques to try. First, don’t get stuck on a single question and waste so much time on it you don’t have a chance to answer other questions.

If you’ve stared at a question for 60 seconds and have no idea how to solve it, skip it and move on. You can always come back to it at the end of the section if you have more time. Second, for many questions, you’ll see some questions that are obviously incorrect. Do yourself a time-saving favor and cross these off in your booklet immediately. The faster you can eliminate wrong answer choices, the faster you can solve for the correct answer.

Finally, one of the best ways to get faster on the ACT is to take lots of practice tests. By doing so you’ll become more familiar with the test and know what to expect and what shortcuts you can use to answer questions.


Question Comprehension Issue

This issue is especially common with people who read questions quickly in hopes of saving time. Even though you’ll be pressed for time on the ACT, spending an extra few seconds to figure out exactly what a question is asking you is well worth your time.

Many students underline key parts of a question to make sure they’re not missing any important information when they read it. This can be particularly helpful for Reading and Science questions, where you’ll need to get your information from long passages. Knowing exactly what you’re looking for can help you save time and ensure you’re looking for the right information.


Procedural/Comprehension Issue

Both of these issues can be solved by building up your knowledge of what the ACT tests and how its questions are worded. For procedural problems, the best way to improve is to answer lot of practice questions so you become familiar with what ACT questions look like. ACT prep books can also give you insight into how to solve questions. For comprehension issues, you can brush up on the content the ACT tests by using class notes, textbooks on the material, or an ACT prep book.


Careless Error

In order to stop making careless errors, you need to figure out what’s causing them in the first place. Were you pressed for time? Then improving your time management skills will help. Did you get tripped up by one of the ACT’s common tricks, like only solving for x  when you were supposed to solve for 2x? Reading prep books to learn common tricks can help you avoid making those mistakes again. Leaving yourself a few minutes at the end of each ACT section to go over your answers can also help you catch any careless mistakes you may have made.




6 Steps to Creating the Best ACT Prep Plan for You

After you’ve taken your ACT diagnostic test and reviewed your results, you can use that information to create your ACT study plan.  Below are the six steps to follow to create a study plan that’ll help you strengthen your weaknesses and get the ACT score you’re aiming for.


#1: Set an ACT Goal Score

Once you have the results from your ACT diagnostic, you need to set a target score so you know what your goal is when you take the actual ACT. To set a target score, first make a list of the colleges you want to apply to. Then find the average ACT scores of admitted students for each of those schools. (This info is usually available on each school’s class profile.) Find the highest average ACT score on your list. That's your goal score because reaching it will give you a good shot at getting into each of your potential schools.

Once you have your goal score, compare it to your diagnostic score. Are they close? Far apart? Are there certain sections where you met your goal score but others where you didn’t? Having this info will help you determine your actions for the rest of the steps in your study plan.


#2: Figure Out How Long You Need to Study

How much you need to study for the ACT depends on the difference between your diagnostic test results and your goal score. Here are our estimates for the total number of hours you'll need to prep based on the ACT score improvement you want:

Composite ACT Points You Want to Improve

Hours of Study Needed

0-1 points

10 hours

1-2 points

20 hours

2-4 points

40 hours

4-6 points

80 hours

6-9 points

150+ hours


Once you know how long you plan on studying, you can decide how many hours you want to study a week and work backwards to figure out how many weeks/months you’ll need to prepare and when you should take the ACT.


#3: Get High-Quality Study Resources

In order to have a great study plan, you’re going to need to use the best study materials out there. We’ve already discussed the importance of using official practice tests when you study for the ACT. Unofficial practice tests can sometimes vary greatly from the real exam, which means you’ll be taking tests that don’t help or, worse, prepare you for the wrong material. Always use official practice ACTs when you can.

A prep book can also be one of the most useful tools for your ACT studying. They can be especially helpful at explaining tricky concepts and breaking down how to solve different types of ACT problems. Check out our guide to the top ACT prep books to learn which are the best prep books out there.


#4: Focus on Your Weaknesses

As we discussed above, it’s important for you to identify your weak areas and prioritize strengthening them. Once you know which subjects or question types you want to improve in, there are several ways to go about doing this:

  • Reviewing content: either in a prep book or school notes
  • Answer practice questions
  • Asking for help if needed: If you’ve read through all your relevant notes on a subject, you may want to try asking a classmate who is also taking the ACT for help or look into getting a tutor.


#5: Take Regular Practice ACTs

Your ACT diagnostic isn’t the only practice test you should take before exam day. Regular practice tests will help you track your progress and get more familiar with the exam. We recommend taking three to six full-length practice ACTs before test day. There are currently five official practice ACTs available for free, so definitely make use of them.


#6: Regularly Check Your Progress

As you study for the ACT, you should regularly step back and analyze how things are going. Are you making the progress you’re wanting? If not, what do you think you should change about your study plan? Are you able to get in the number of study hours you want to? Where are you still struggling? How can you fix that issue?

This is a key step to follow because if something’s not working, you’re not going to see the improvements you want, no matter how often you keep doing it. If you’re stuck you might consider looking at tutors or reading our list of the 18 best tips for the ACT to get some new study ideas.


What's Next?

Ready to get a perfect ACT score? Read our famous guide on what it takes, written by an expert 36 scorer.

Looking for more ACT practice tests? Check out our massive collection of official and unofficial ACT practice tests.

Not sure when you should take the ACT? Get a complete study plan for the ACT to figure out the best date for you.


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Christine Sarikas
About the Author

Christine graduated from Michigan State University with degrees in Environmental Biology and Geography and received her Master's from Duke University. In high school she scored in the 99th percentile on the SAT and was named a National Merit Finalist. She has taught English and biology in several countries.

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